title: Decomposition of slide helix contributions to ATP-dependent inhibition of Kir6.2 channels.
abstract: Regulation of inwardly rectifying potassium channels by intracellular ligands couples cell membrane excitability to important signaling cascades and metabolic pathways. We investigated the molecular mechanisms that link ligand binding to the channel gate in ATP-sensitive Kir6.2 channels. In these channels, the "slide helix" forms an interface between the cytoplasmic (ligand-binding) domain and the transmembrane pore, and many slide helix mutations cause loss of function. Using a novel approach to rescue electrically silent channels, we decomposed the contribution of each interface residue to ATP-dependent gating. We demonstrate that effective inhibition by ATP relies on an essential aspartate at residue 58. Characterization of the functional importance of this conserved aspartate, relative to other residues in the slide helix, has been impossible because of loss-of-function of Asp-58 mutant channels. The Asp-58 position exhibits an extremely stringent requirement for aspartate because even a highly conservative mutation to glutamate is insufficient to restore normal channel function. These findings reveal unrecognized slide helix elements that are required for functional channel expression and control of Kir6.2 gating by intracellular ATP.
authors.affiliation: Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
authors.forename: Jenny B W
authors.initials: JB
authors.lastname: Li
authors.forename: Xinyang
authors.initials: X
authors.lastname: Huang
authors.forename: Roger S
authors.initials: RS
authors.lastname: Zhang
authors.forename: Robin Y
authors.initials: RY
authors.lastname: Kim
authors.forename: Runying
authors.initials: R
authors.lastname: Yang
authors.forename: Harley T
authors.initials: HT
authors.lastname: Kurata
mesh_terms: D000255:Adenosine Triphosphate / Q000235:genetics / Q000378:metabolism*; D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D051379:Mice; D020125:Mutation, Missense; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D000099161:Kcnj11 Channel
chemical_list: D000255:Adenosine Triphosphate; D024661:Potassium Channels, Inwardly Rectifying; D000099161:Kcnj11 Channel
keywords: Electrophysiology; Inward Rectifier Channel; Ion Channels; KATP Channel; Membrane Biophysics; Potassium Channels; Protein Engineering